Why do winemakers use oak barrels to age wine? And why is oak the preferred wood?
Literature and archaeology both offer proof that we've been making wine for roughly 5,000 years. And our efforts to try to preserve it probably started soon after that first vintage.
On Cyprus, 5,000- to 5,500-year-old wine jugs have been dug up, and Homer's Iliad and Odyssey, composed nearly 3,000 years ago, both mention the "wine-dark sea." The original vessels we have - simple pottery jugs - were better than nothing, but by 2,000 years ago, someone had a better idea.
Pliny the Elder mentions that people in the Alps of northern Italy-southern France were storing wine in wooden barrels in the first century A.D. The first use of oak, whether it was then or later, was likely more a matter of convenience than genius, since oak forests were common in central and western Europe.
Over the centuries, plenty of other woods have been tried. The Greeks' fondness for retsina, their resin-flavored wine, may have come from pine barrels, although they actually inject pine resin into their wines these days rather than aging them in pine. Chestnut also has been and still is used in the Rhone region of France. In Chile, beech used to be popular. Sotheby's Wine Encyclopedia notes La Palma in the Canary Islands still ages "Tea Wine" in pine barrels. And winemakers in California and Oregon have used redwood. I recall seeing some huge redwood tanks in the mid-1970s at a winery near Livermore, Calif.
Oak has two important benefits for wine, notes Rob Griffin, owner-winemaker of Barnard Griffin Winery in Richland, Wash., and one of the deans of Northwest winemaking.
First, an oak barrel allows the controlled introduction of oxygen to allow proper aging.
And second, oak introduces all those wonderful wood-related flavor components we enjoy in most red wines and in many whites.
The tannins from toasted oak barrels help preserve the wine and add to its mouth feel. The phenols add spicy and smoky aromas that create a pleasing complexity. And the wood also allows a certain amount of evaporation, especially of alcohol, which helps mellow the wine.
And even when the wine has absorbed almost all the flavors and aromas we regard so highly, an oak barrel still benefits red wine, Griffin said.
That's one reason he has gigantic European oak storage tanks that are about four decades old that came out of Joseph Phelps Winery in California. "If you have red wine, it still is better off in wood than if you put it in stainless steel because wine in stainless is much more likely to be attacked by molds" and similar organisms, he said.
No other wood seems to offer all those attractions.
When winemaking shifted to the New World, the oak forests of the United States offered a new share of complexity and debate to the process of aging and preserving wine.
To many, especially European winemakers and wine drinkers, American oak is felt to be a bit too coarse, too abrupt, too "obvious," as Tom Stevenson, the author of Sotheby's Wine Encyclopedia put it.
But those who love oakiness, especially the delightful vanilla and coconut elements of American oak, find it more appealing than the more subtle European varieties.
The differences between the two types have been accentuated by the way in which they are turned into barrels. European oak logs generally are split into barrel staves. American oak generally is sawed in a process that produces roughly a fifth more staves from a log.
Sawing a log also breaks down more cells in the wood, releasing more vanillin and other elements that impart coconut-like flavors. Combine sawed wood with American oak's naturally more open grain structure and more "woody" elements end up in the wine.
In addition, American oak is usually kiln dried, while European oak is air dried. Stevenson notes that kiln drying produces "more aggressive" tannins and leaves in the wood some of the aromatic compounds leached out during air drying.
Wine Words: Bousinage
What would we do without the French to provide us all their wonderfully precise and mysterious words that allow us English-only sorts to practice our fractured Franglais?
Bousinage is the word for the process of toasting the inside of an oak barrel, the degree of "toast" applied to a barrel's inner surface. The toasting provides several elements key to the enjoyment of wine lovers who gush over nicely oaked Chardonnay, Cabernet Sauvignon, Merlot and all those other wonderful reds.
And here, I can't resist quoting directly from the Wine Encyclopedia: "During toasting, furanic aldehydes (responsible for 'roasted' aromas) reach their maximum concentration, the vanilla aroma of vanillin is heightened, and various phenols, such as eugenol (the chief aromatic constituent of oil of cloves), add a smoky, spicy touch to the complexity of oak aromas in wine."
For those of us who aren't chemists, it's probably enough to know that there are three degrees of toast - light, medium and heavy.
Surprisingly, the medium-heavy and heavy toast barrels often are used for Chardonnay (and bourbon), partly because they remove the color from red wines. So a light-medium toast is more likely to end up holding most red wines.
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